[jQuery] Most basic of basic fundamental questions.

[Pickledegg]

I'm reading 'learning jQuery'. In this example, and in fact every
example, why do you pass a function as an argument.

$(document).ready(function() {
$('.poem-stanza').addClass('emphasized');
});

why can't I do this?

$(document).ready(
$('.poem-stanza').addClass('emphasized');
);

Thanks. I'm asking this a learning exercise, so I apologize in advance
for the apparent stupidity of it.